3D integrated circuit stack-wide synchronization circuit

ABSTRACT

There is provided a synchronization circuit for a 3D chip stack having multiple circuits and multiple strata interconnected using a first and a second stack-wide broadcast connection chain. The synchronization circuit includes the following, on each stratum. A synchronizer connected to the first connection chain receives an asynchronous signal therefrom and performs a synchronization to provide a synchronous signal. A driver is connected to the second chain for driving the synchronous signal. A latch connected to the second chain receives the synchronous signal driven by the driver on a same or different stratum within a next clock cycle from the synchronization to provide the stack-wide synchronous signal to a circuit on a same stratum. An output of a single driver on one stratum is selected at any given time for use by the latch on all strata.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional application of co-pending U.S. patentapplication Ser. No. 13/217,767 filed on Aug. 25, 2011, incorporatedherein by reference in its entirety.

This application is related to the following commonly assignedapplications, all filed on Aug. 25, 2011 and incorporated herein byreference: U.S. application Ser. No. 13/217,734, entitled “PROGRAMMINGTHE BEHAVIOR OF INDIVIDUAL CHIPS OR STRATA IN A 3D STACK OF INTEGRATEDCIRCUITS”; U.S. application Ser. No. 13/217,335, entitled “SYNCHRONIZINGGLOBAL CLOCKS IN 3D STACKS OF INTEGRATED CIRCUITS BY SHORTING THE CLOCKNETWORK”; U.S. application Ser. No. 13/217,349, entitled “3D CHIP STACKSKEW REDUCTION WITH RESONANT CLOCK AND INDUCTIVE COUPLING”; U.S.application Ser. No. 13/217,789, entitled “CONFIGURATION OF CONNECTIONSIN A 3D STACK OF INTEGRATED CIRCUITS”; U.S. application Ser. No.13/217,381, entitled “3D INTER-STRATUM CONNECTIVITY ROBUSTNESS”; U.S.application Ser. No. 13/217,406, entitled “AC SUPPLY NOISE REDUCTION INA 3D STACK WITH VOLTAGE SENSING AND CLOCK SHIFTING”; and U.S.application Ser. No. 13/217,429, entitled “VERTICAL POWER BUDGETING ANDSHIFTING FOR 3D INTEGRATION”.

BACKGROUND

1. Technical Field

The present invention relates generally to integrated circuits and, inparticular, to a 3D integrated circuit stack-wide synchronizationcircuit.

2. Description of the Related Art

A three-dimensional (3D) stacked chip includes two or more electronicintegrated circuit chips (referred to as strata or stratum) stacked oneon top of the other. The strata are connected to each other withinter-strata interconnects that could use C4 or other technology, andthe strata could include through-Silicon vias (TSVs) to connect from theactive electronics on one side of the stratum to the opposite side ofthe stratum. The active electronics can be on the “front” or “back” sideof the stratum.

In a 3D integrated stack, all strata may operate synchronously from agiven clock source. For some operations, it is required that anasynchronous signal, originating outside of the stack, trigger asynchronized operation with all strata of the stack. A “strobe” and a“start” operation are examples of such operations. This synchronizationmust occur regardless of process or parameter or temperature or voltagevariations across the stack.

SUMMARY

According to an aspect of the present principles, there is provided astack-wide synchronization circuit for providing a stack-widesynchronous signal to each stratum of a 3D chip stack having multiplecircuits and two or more strata interconnected using at least a firstand a second connection chain. Each of the first and the secondconnection chains are in a stack-wide broadcast configuration. Thestack-wide synchronization circuit includes the following, on each ofthe two or more strata. A synchronizer is connected to the firstconnection chain for receiving an asynchronous signal therefrom andperforming a synchronization of the asynchronous signal to a clocksignal to provide a synchronous signal with respect to the clock signal.A driver is connected to the second connection chain for driving thesynchronous signal. A latch is connected to the second connection chainfor receiving the synchronous signal driven by the driver on a same oneor a different one of the two or more strata within a next clock cyclefrom the synchronization to provide the stack-wide synchronous signal toat least one of the multiple circuits on a same one of the two or morestrata. The driver on each of the two or more strata is configured suchthat an output of a single driver on one of the two or more strata isselected at any given time for use by the latch on all of the two ormore strata.

According to another aspect of the present principles, there is provideda method for providing a stack-wide synchronous signal to each stratumof a 3D chip stack having multiple circuits and two or more stratainterconnected using at least a first and a second connection chain.Each of the first and the second connection chains are in a stack-widebroadcast configuration. The method includes providing the following oneach of the two or more strata. A synchronizer is provided connected tothe first connection chain and configured to receive an asynchronoussignal therefrom and perform a synchronization of the asynchronoussignal to a clock signal to provide a synchronous signal with respect tothe clock signal. A driver is provided connected to the secondconnection chain and configured to drive the synchronous signal. A latchis provided connected to the second connection chain and configured toreceive the synchronous signal driven by the driver on a same one or adifferent one of the two or more strata within a next clock cycle fromthe synchronization to provide the stack-wide synchronous signal to atleast one of the multiple circuits on a same one of the two or morestrata. The method further includes configuring the driver on each ofthe two or more strata such that an output of a single driver on one ofthe two or more strata is selected at any given time for use by theinter-strata receiver on all of the two or more strata.

According to yet another aspect of the present principles, there isprovided a method for providing a stack-wide synchronous signal to eachstratum of a 3D chip stack having multiple circuits and two or morestrata interconnected using at least a first and a second connectionchain. Each of the first and the second connection chains are in astack-wide broadcast configuration. The method includes the followingwith respect to each of the two or more strata. An asynchronous signalis received. A synchronization is performed of the asynchronous signalto a clock signal to provide a synchronous signal with respect to theclock signal. The synchronous signal driven by the driver on a same oneor a different one of the two or more strata is received. Thesynchronous signal is latched within a next clock cycle from thesynchronization to provide the stack-wide synchronous signal to at leastone of the multiple circuits on a same one of the two or more strata.The driver on each of the two or more strata is configured such that anoutput of a single driver on one of the two or more strata is selectedat any given time to provide the synchronous signal on each of the twoor more strata for said step of receiving the synchronous signal.

According to still another aspect of the present principles, there isprovided a stack-wide synchronization circuit for synchronizing anasynchronous signal in each stratum of a 3D chip stack having two ormore strata interconnected using at least a first and a second chain ofvias. Each of the first and the second chain of vias are in a stack-widebroadcast configuration. The stack-wide synchronization circuit includesthe following on each of the two or more strata. A first connectionpoint is for receiving the asynchronous signal. An off-chip receiver hasan input and an output, the input connected to the connection point. Anasynchronous-to-synchronous signal converter has an input connected toan output of the off-chip receiver. A tri-state driver has anon-selection input connected an output of theasynchronous-to-synchronous signal converter. A second connection pointis connected to an output of the tri-state driver. An inter-stratareceiver has an input connected to the second connection point. Astaging latch has an input connected to an output of the inter-stratareceiver. The first connection point is connected to the first chain ofvias and the second connection point is connected to the second chain ofvias. The tri-state drivers are configured such that an output of asingle tri-state driver on one of the two or more strata is selected atany given time. The output of the staging latch on each of the two ormore strata provides a stack-wide synchronous signal during a givenclock cycle responsive to a receipt of the asynchronous input signal bythe first connection point on any of the two or more strata during animmediately preceding clock cycle with respect to the given clock cycle.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1 shows a stack-wide synchronization circuit 100 for a 3D chipstack 199, in accordance with an embodiment of the present principles;

FIG. 2 further shows a synchronizer 200 and corresponding selectioncircuit 250 to which the present principles may be applied, inaccordance with an embodiment of the present principles; and

FIG. 3 shows a method 300 for providing a stack-wide synchronous signalin a 3D chip stack, in accordance with an embodiment of the presentprinciples.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present principles are directed to a 3D integrated circuitstack-wide synchronization circuit. That is, the present principlesprovide a circuit configuration that provides a robust stack-widesynchronization function. Moreover, the present principles also providea synchronization function when a single stratum is being tested priorto construction into a 3D stack.

Each stratum in the stack will include an off-chip receiver to receivean asynchronous input signal broadcast to all strata from off-chip. Thisasynchronous input signal will be synchronized on each stratum to thestrata clock using known circuits. Stack configuration logic willdesignate one stratum as the synchronization master who will broadcastthe synchronized signal to all strata where they are received within oneclock cycle. This signal is then staged in each stratum resulting instack-wide synchronization.

FIG. 1 shows a stack-wide synchronization circuit 100 for a 3D chipstack 199, in accordance with an embodiment of the present principles.Each stratum has an equivalent circuit portion 101 of the stack-widesynchronization circuit in order to provide stack-wide asynchronous tosynchronous conversion.

The 3D chip stack 199 includes the following strata: a stratum 190; astratum 191; and a stratum 192. Such strata may be interconnected usingC4 connections (C4) 177 and through-and-through type through-Siliconvias (TSVs) 176A and 176B. Of course, other chip-to-chip interconnectsmay also be used, while maintaining the spirit of the presentprinciples. Through-and-through type TSVs 176A and 176B are described infurther detail in the aforementioned related application, namely Ser.No. 13/217,789, entitled “Configuration of Connections in a 3D stack ofIntegrated Circuits”.

The 3D chip stack 199 includes asynchronous input points 110. Suchasynchronous input points 110 may include, for example, probe pads 178,and C4 connections 177. Moreover, such asynchronous input points 110 areinter-connected across the strata using the through-and-through TSVs176A which can include one or more C4 connections 177.

The asynchronous input points 110 are also connected to a respectiveoff-chip signal receiver 122 on each stratum. The off-chip receiver 122on each stratum is part of a chain of elements on each stratum (andinterconnected across the strata as described below) that enable thestack-wide synchronization described herein. Each off-chip signalreceiver 122, in turn, is connected to an asynchronous-to-synchronoussignal conversion circuit (hereinafter “synchronizer” for the sake ofbrevity) 123. Each synchronizer 123 may provide an amount of “de-bounce”for an asynchronous input signal, for example.

Further regarding the synchronizers 123, each of same receives theasynchronous input signal and a clock signal. Each synchronizer 123 thenoutputs a signal which has the signal value of the asynchronous inputsignal, but synchronized to the clock signal. That is, when theasynchronous input signal changes, then the output of each synchronizer123 will change to the value of the changed asynchronous input signal,at a time that is related to an edge of the clock signal. Nonetheless,while the signals output from the synchronizers 123 are synchronous withrespect to the clock signal, the outputs from the synchronizers 123 ondifferent strata may be aligned to different clock pulses due tovariations in the delay of the circuits on one stratum compared toanother. Accordingly and advantageously, the present principles providea way to synchronize these signals from the synchronizers 123 on astack-wide-basis.

The stack-wide synchronization circuit 100 includes, on each of thestrata, a probe pad 178, (at least two) connection points 121 and 129,portions (respective ends) of (at least two) through-and-through TSVs176A and 176B and C4 connections 177, an off-chip receiver 122, asynchronizer 123, a programmable tri-state driver 124, and inter-stratainput/output (I/O) receiver 125, and a staging latch 126.

For each stratum, the preceding elements are connected as follows. Theprobe pad 178 is connected to the connection point 121. The connectionpoint 121 is also connected to an input of the off-chip receiver 122. Anoutput of the off-chip receiver 122 is connected to an input of thesynchronizer 123. An output of the synchronizer 123 is connected to an(non-selection) input of the tri-state driver 124. An output of thetri-state driver 124 is connected to the connection point 129. Theconnection point 129 is also connected to an input of the inter-stratareceiver 125. An output of the inter-strata receiver 125 is connected toan input of the staging latch 126. An output of the staging latch 126 isconnected to a pad or a circuit on that same stratum (with the pad orstratum represented by the reference numeral 179). Moreover, theconnection point 121 is connected to a through-and-through TSV 176A andone or more C4 connections 177 placed and connected in an inputbroadcast configuration (so as to provide a broadcast or pass-throughfunction throughout the stack 199 for the asynchronous input signal).Similarly the connection point 129 is connected to a through-and-throughTSV 176B and one or more C4 connections 177 placed and connected in abroadcast configuration (so as to provide a broadcast or pass-throughfunction throughout the stack 199 for the synchronous signal initiallyoutput from selected synchronizer 123). As noted above, this synchronoussignal is synchronous to the clock signal provided to the synchronizer123 for the purpose of synchronization thereto, but each the synchronoussignals output from the synchronizers 123 may not be synchronous acrossthe stack.

Regarding the tri-state driver 124, the same receives a stackconfiguration program bit (denoted as “P1”, “P2”, and “P3” in FIG. 1)via a selection input thereof. The tri-state driver 124 is sized, andthe placement and wiring is adjusted such that a signal from the outputof the synchronization circuit 123 on one stratum will reach the staginglatch 126 on any other stratum in time to be received on the edge of thenext clock signal on that (other) stratum. Once the system is programmedsuch that only one of the above tri-state drivers 124 is enabled, anasynchronous signal provided to the stack 199 (or to the input of a lonestratum) will cause a stack-wide synchronous rise of a signal at theoutput of the staging latch 126.

Stack configuration logic (not shown) will designate one stratum as thesynchronization master that will broadcast the synchronized signal toall strata where the synchronized signal is received within one clockcycle. This signal is then staged by the staging latch 126 on eachstratum resulting in stack-wide synchronization.

It is to be appreciated that the synchronization function can beprovided to each single stratum separately when such single stratum isbeing tested prior to construction into a 3D stack (such as stack 199).

It is to be further appreciated that off-chip receiver 121 andinter-stratum receiver 125 are simply conventional receivers, but arecapable of receiving off-chip provided signals (in the case of receiver121) and inter-stratum provided signals (in the case of receiver 125)due to their respective configurations in the stack-wide synchronizationcircuit 100, as would be readily appreciated by one of ordinary skill inthe art.

FIG. 2 further shows a synchronizer 200 and corresponding selectioncircuit 250 to which the present principles may be applied, inaccordance with an embodiment of the present principles. Thesynchronizer 200 may be used for synchronizer 123 shown and describedwith respect to FIG. 1. However, it is to be appreciated that thepresent principles are not limited solely to using synchronizer 200, asother types and configurations of a synchronizer may also be readilyused in accordance with the present principles, while maintaining thespirit of the present principles.

The synchronizer 200 includes a multiplexer 210 having three datainputs, two selection inputs, and an output. The output of themultiplexer 210 is connected to an input of a clock triggered latch 220.An output of the clock triggered latch 220 provides a synchronizedsignal (tck_sync_stratum) synchronized with a clock signal (nclk).

The selection input of the multiplexer 210 is provided a selectionsignal from a selection circuit 250. Of course, in other embodiments, adifferent selection circuit may be used. These and other variations arereadily contemplated by one of ordinary skill in the art, whilemaintaining the spirit of the present principles. The selection circuit250 includes a first clock triggered latch 261 and a second clocktriggered latch 262 having an input connected to an output of the firstclock triggered latch 261. The first clock triggered latch 261 receivesan asynchronous signal (tck_async). The second clock triggered latch 262receives the synchronous output of the first clock triggered latch 261.Hence, when the asynchronous input is at logic LO for two adjacent clockcycles, the outputs of both latches 261 and 262 will be ‘0’. This causesthe multiplexer 210 to output a ‘0’ which in turn will be captured inthe latch 220 producing a clock synchronized ‘0’ output astck_symc_stratum. When the asynchronous input tck_async is at logic HIor ‘1’ for two adjacent clock cycles, the outputs of both latches 261and 262 will be ‘1’. This causes the multiplexer 210 to output a ‘1’which in turn will be captured in the latch 220 producing a clocksynchronized ‘1’ output as tck_sync_stratum. If the asynchronous inputis changing from clock cycle to clock cycle, then the multiplexer 210will cause the last value stored in the latch 220 to be held. Variousperturbations of this circuits are possible. For example, more latchesin the configuration of 261 and 262 may be added to provide moreasynchronous noise rejection. Also, the operation of the multiplexer maybe changed such that the tck_sync_stratum signal is a synchronous pulsethat is output when an asynchronous rise or fall is detected.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

Aspects of the present invention are described below with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

Reference in the specification to “one embodiment” or “an embodiment” ofthe present principles, as well as other variations thereof, means thata particular feature, structure, characteristic, and so forth describedin connection with the embodiment is included in at least one embodimentof the present principles. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment”, as well any other variations,appearing in various places throughout the specification are notnecessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This may be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

It is to be further appreciated that while one or more embodimentsdescribed herein may refer to the use of Silicon with respect to a chipor a through via, the present principles are not limited to using onlychips or vias made from Silicon and, thus, chips or vias made from othermaterials including but not limited to Germanium and Gallium Arsenidemay also be used in accordance with the present principles whilemaintaining the spirit of the present principles. Moreover, it is to befurther appreciated that while one or more embodiments described hereinmay refer to the use of C4 or micro C4 (uC4) connections, the presentprinciples are not limited to solely using C4 or micro C4 connectionsand, thus, other types of connections may also be used while maintainingthe spirit of the present principles.

It is to be understood that the present invention will be described interms of a given illustrative architecture having a wafer; however,other architectures, structures, substrate materials and processfeatures and steps may be varied within the scope of the presentinvention.

It will also be understood that when an element as a layer, region orsubstrate is referred to as being “on” or “over” another element, it canbe directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “connected” or “coupled” to another element, it canbe directly connected or coupled to the other element or interveningelements may be present. In contrast, when an element is referred to asbeing “directly connected” or “directly coupled” to another element,there are no intervening elements present.

A design for an integrated circuit chip of photovoltaic device may becreated in a graphical computer programming language, and stored in acomputer storage medium (such as a disk, tape, physical hard drive, orvirtual hard drive such as in a storage access network). If the designerdoes not fabricate chips or the photolithographic masks used tofabricate chips, the designer may transmit the resulting design byphysical means (e.g., by providing a copy of the storage medium storingthe design) or electronically (e.g., through the Internet) to suchentities, directly or indirectly. The stored design is then convertedinto the appropriate format (e.g., GDSII) for the fabrication ofphotolithographic masks, which typically include multiple copies of thechip design in question that are to be formed on a wafer. Thephotolithographic masks are utilized to define areas of the wafer(and/or the layers thereon) to be etched or otherwise processed.

Methods as described herein may be used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

FIG. 3 shows a method 300 for providing a stack-wide synchronous signalin a 3D chip stack, in accordance with an embodiment of the presentprinciples. By method 300, the stack-wide synchronous signal is providedto each stratum of a 3D chip stack having multiple circuits and two ormore strata interconnected using at least a first and a secondconnection chain. Each of the first and the second connection chains isin a stack-wide broadcast configuration. Steps 310 through 370 areperformed for each of the two or more strata.

At step 310, a receiver is provided, connected to the first connectionchain, configured to receive an asynchronous signal.

At step 320, a synchronizer is provided configured to perform asynchronization of the asynchronous signal to a clock signal to providea synchronous signal with respect to the clock signal.

At step 330, a driver is provided, connected to the second connectionchain, configured to drive the synchronous signal.

At step 340, an inter-strata receiver is provided, connected to thesecond connection chain, configured to receive the synchronous signaldriven by the driver on the same one or a different one of the two ormore strata,

At step 350, a latch is provided, connected to the inter-stratareceiver, configured to receive the synchronous signal within a nextclock cycle from the synchronization to provide the stack-widesynchronous signal to at least one of the multiple circuits on the sameone of the two or more strata.

At step 360, the driver on each of the two or more strata is configuredsuch that the output of a single driver on one stratum is selected atany given time for use by the inter-strata receiver on all strata.

At step 370, one or more programming bits are provided to the drivers inorder to select a master stratum by selecting only one of the drivers ona given one (i.e., the master) of the two or more strata, such that theoutput of the selected single driver is provided to the inter-stratareceiver on each of the two or more strata for use in providing thestack-wide synchronous signal from each latch on each stratum.

At step 380, an asynchronous input signal is provided to any one of theasynchronous signal inputs in order to obtain the stack-wide synchronoussignal at the output of each latch on each stratum.

This circuit is an element of a 3D IC and as such requires other 3Delements that are either known, or disclosed separately. In oneembodiment, this can include inter-strata interconnections, both of thethrough and through type, and of the disjoint type. Of course, othertypes of connections performing the same functions may also be used,while maintaining the spirit of the present principles. Moreover, it isto be appreciated that the present principles could also be programmedby a system described separately that configures individual stratum in a3D stack of integrated circuits. These and other variations andimplementations of the present principles are readily ascertained fromone of ordinary skill in the art given the teachings of the presentprinciples provided herein, while maintaining the spirit of the presentprinciples.

Having described preferred embodiments of a system and method (which areintended to be illustrative and not limiting), it is noted thatmodifications and variations can be made by persons skilled in the artin light of the above teachings. It is therefore to be understood thatchanges may be made in the particular embodiments disclosed which arewithin the scope of the invention as outlined by the appended claims.Having thus described aspects of the invention, with the details andparticularity required by the patent laws, what is claimed and desiredprotected by Letters Patent is set forth in the appended claims.

What is claimed is:
 1. A stack-wide synchronization circuit forsynchronizing an asynchronous signal in each stratum of a 3D chip stackhaving two or more strata interconnected using at least a first and asecond chain of vias, each of the first and the second chain of viasbeing in a stack-wide broadcast configuration, the stack-widesynchronization circuit comprising, on each of the two or more strata: afirst connection point for receiving the asynchronous signal; anoff-chip receiver having an input and an output, the input connected tothe connection point; an asynchronous-to-synchronous signal converterhaving an input connected to an output of the off-chip receiver; adriver having a non-selection input connected an output of theasynchronous-to-synchronous signal converter; a second connection point,connected to an output of the driver; an inter-strata receiver having aninput connected to the second connection point; and a latch having aninput connected to an output of the inter-strata receiver, wherein thefirst connection point is connected to the first chain of vias and thesecond connection point is connected to the second chain of vias, thedrivers are configured such that an output of a single driver on one ofthe two or more strata is selected at any given time, and wherein theoutput of the latch on each of the two or more strata provides astack-wide synchronous signal during a given clock cycle responsive to areceipt of the asynchronous input signal by the first connection pointon any of the two or more strata during an immediately preceding clockcycle with respect to the given clock cycle.
 2. The stack-widesynchronization circuit of claim 1, wherein the driver on each of thetwo or more strata is responsive to one or more programming bits thatspecify the single selected driver.
 3. The stack-wide synchronizationcircuit of claim 1, wherein the driver is a tri-state driver.
 4. Thestack-wide synchronization circuit of claim 1, wherein the driver is amultiplexer.
 5. The stack-wide synchronization circuit of claim 1,further comprising, on each of the two or more strata, an asynchronousinput point connected to the first connection point.
 6. The stack-widesynchronization circuit of claim 1, wherein the asynchronous input pointcomprises at least one of input pads and C4 connections.
 7. Thestack-wide synchronization circuit of claim 1, wherein theasynchronous-to-synchronous signal converter, the driver, and the latchon the same one of the two or more strata are serially connected in achain having as taps the first chain of vias and the second chain ofvias.